The present invention relates to a bayonet mount adapter for a camera of the interchangeable lens type.
The bayonet system and the screw-in system are commonly employed for mounting interchangeable lenses to cameras. As is well-known, the use of a bayonet mount adapter having an internal thread adapted for a screw-in lens mount and also having an external catch adapted to secure a bayonet mount in position enables the mounting of a lens barrel of the screw-in type to a camera body of the bayonet mount type.
A method currently adopted in a camera of the bayonet mount type for securing a bayonet type lens in position is to arrange a manually operable lock pin on the mount surface on the camera side and to cut a groove or recess in the mount surface on the lens side for entrapping the lock pin. In this mechanism, the locked lens is released by manually actuating the lock pin externally of the mount surface.
When attaching a bayonet mount adapter to a camera of the bayonet mount type, the bayonet mount adapter may be secured to the camera body in a manner similar to the attachment of the bayonet type lens by engaging the lock pin on the camera side into a groove or recess cut in the adapter. Thus a screw-in lens may be secured to the camera body by screwing it into the previously secured mount adapter. This method, however, is disadvantageous in that the thickness of the adapter flange is added to the flange back (or mechanical back) of the camera body. Specifically, the screw-in type lens is operative only when the mechanical back thereof is larger than that of the associated camera body. In order to avoid the foregoing problem, the thickness of the mount adapter flange may effectively be reduced to zero by bringing the mount reference plane of the screw-in lens into the same plane as the mount reference plane of the camera body.
The above-mentioned method is disclosed in Japanese Utility Model Publication 1974-2,200, wherein the flange portion of the mount adapter can be received in a space axially defined between the front surface and mount surface of a known bayonet mount on the camera side, so that the mechanical back of the screw-in type lens is brought into the same plane as the mechanical back of the camera body to thereby allow a photographing operation. However, in a camera having a mount lock pin arranged in the mount reference plane, the adapter is received in the mount reference plane and therefore cannot be secured unrotatingly.
It is therefore an object of this invention to provide means for securing the mount adapter unrotatingly. According to this invention a lock member is arranged on the mount adapter so that the mount adapter can be locked positively without using the lock mechanism on the camera side, thereby permitting the use of a screw-in type lens.
The bayonet mount adapter of this invention is so constructed that it can be received in the bayonet mount on the camera side in either the same plane as or in a slightly lower plane (0.1 - 0.2mm) than the mount reference plane as measured in the axial direction of the bayonet mount washer on the camera side. The mount adapter carries a leaf spring on its outer circumferential surface so that, when it is fitted into the bayonet on the camera side, the leaf spring is engaged with the projection formed on the bayonet on the camera side to thereby prevent the adapter from rotating and loosening. When removing the adapter from the camera body, the engagement between the leaf spring and projection can be released manually at the top or exposed forward surface of the adapter.